Screw-propeller



' UNITED STATES PATENT OFFICEo HAEEIsoN o. rEAEsoNs, 0E 'EEEEYsEUEaMICHIGAN.

soREwPRoPELLER- SPECIFICATION forming part of Letters .Patent No.293,777, dated February 19, 1884. Application filed January 15, 1883,l(Model.)

To all whom t 'may concern.-

Be it known 'that I, HAEEIsoN G. PEAR! soNs, of Ferrysburg, in thecounty of Ottawa and State of Michigan, have invented new and usefulImprovements in Screw-Propellers; and I hereby declare that thefollowing is a full, clear, and exact description thereof, referencebeing had to the accompanying drawings, which form a part of thisspecification.

This invention relates to certain new and useful improvements in theconstruction of screw-blades for propellers, the object of the inventionbeing to utilize a portion of the great amount of power that is lost bythe present construction, and the invention consists in the peculiarconstruction of the blade, as hereinafter more fully described, and thenpointed outin the claim.

Figure 1 is a perspective view of my propeller. Fig. 2 is a'sectionalend view of the same through the line Jv x of Fig. 1. Fig. 3 is asection of one of the blades, obtained Vby the intersection with acylinder and thenl developed on a plane, showing my improve ment Bysharpening the blade on the after or working edge, as illustrated inFig. 3, and constructing the working-face with a convex surface, Iobtain useful work with less friction and resistance due to the bladefrom all the power applied to the wheel than has ever before beenaccomplished. Conceive the blades of a propeller-wheel constructed aftermy improvement to be intersected by a lcylinder whose axis is coincidentwith the center'of the shaft on which the wheel turns, and let thesection of one of the blades be developed on a plane, as shown in Fig.3. Through the after edge,- A, of the blade draw the line A Bperpendicular to the shaft or in the plane of the wheels motion'. Thendraw from the forward edge, C, the line B O parallelwith the shaft. Wehave in BGthe pitch of the wheel corresponding to the width of oneblade. Then, if

y from the point C We set down the amountof slip to D and join A D, weshall' have in A D what Inay be called the line of motion-- that is tosay, by the combined endwise motion of the Wheel, every point in thesection will revolve in a helix, which, when developed on a plane', willbe strictly parallel with the line A D, and inthe line. B D we have thenet pitch corresponding to the width of one blade. It is the negativeresistance due to the thickness ofthe blade that I Wish to get rid of,as

vthis is a very important part of the total work of the wheel; and thisI accomplish by constructing the forward face of the blade with a convexsurface, or on the curve of a parabola, or are of a circle of largeradius, 4and so arranged as to be tangent to the line of motion at theforward edge of the blade, whereby the angle of resistance is at aminimum, as the direct resistance against the motion of the blade inedge is less and the component promoting the forward motion of thevessel is greater as the angle between the line drawn parallel to theline of motion, and at the same time tan gent to the upper convexsurface at its forward edge, andthe line drawn tangentto the sharpenedafter side ata point midway of the thickness of the blade, is less.

I am aware of English Patents Nos. 12,020 of 1848, 2,671 of 1853, and1,376 of 1855, and make no claim to the constructions shown therein.

What I claim as new is A propeller-wheel blade sharpened on the aftersideat the forward or leading edge, and having its forward sidevconstructed with a convex surface, so as to make it tangent to the lineof motion7 at the forward edge of the blade, substantially as and forthe purpose set forth.

i HARRISON C. Witnesses: v A

'0. A. PEARsoN, B. F. GUETIss.

PE ARSONS.

